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Topic Review (Newest First)

11-05-2014 03:30 AM

Hoppy

It will work reasonably well as long as you have a good idea what angle to use as the optic cone angle, and if you have good data on the lumen output at the current you will be using. The cone angle is the hardest one to guess at unless you are using optics.

11-04-2014 05:23 PM

ybendek

Another question guys.... could this work good with cheap LEDs? I mean, for example other cool whit LED with 200 Lm.

If I wanted to try this calculator problem again I would use an empirical approach to get the PAR results for individual LEDs, then use a theoretical approach to get the total PAR for various arrays of those LEDs. It isn't easy to do this, but the results would likely be more accurate. But, I don't plan to do this, and I think several others have already done it. They just haven't made their results widely available and in an easy to use format.

Hoppy.... thank you so much for this tool, I understand ...

11-01-2014 09:01 PM

Hoppy

If I wanted to try this calculator problem again I would use an empirical approach to get the PAR results for individual LEDs, then use a theoretical approach to get the total PAR for various arrays of those LEDs. It isn't easy to do this, but the results would likely be more accurate. But, I don't plan to do this, and I think several others have already done it. They just haven't made their results widely available and in an easy to use format.

11-01-2014 05:54 PM

skanderson

one thing to add is that the new idea in reef lights is to add lime leds because the whites are low in that part of the spectrum. I think that a simple 4k/7k mix looks decent. the tank pictured below is a 65 hex with one 30 watt 4k bridgelux bxra and 4 3 watt cree 7k xmls for a total of 43 watts. its just a grow out tank in my fishroom but the plants are growing fast and coloring well.

Bump: wrong picture above that is of my frag tank and sump lit by only 4k bxras. the 65 hex pic is here.

The calculator is based on using white LEDs only, and they tend to produce about the same lumens for every version of white. If you add in a lot of red/blue, etc, LEDs the calculator won't give good results. This is an empirical calculator, not a theoretical one. It is based on using a variety of data and finding an equation which works well enough with all of the data.

This is an inherent problem with LED calculations.

The more light type variables you add, the messier things start to get. There's much less consistency since you can DIY so many options.

Still, you can get reasonably close with the Whites, then go from there when you add say a set ratio of red and blue mixed with a % of the white.

Say 10% blue, 50% red, 40% white.

Seems that most of the blue types will be close to one another(I would assume), and likewise the same for the reds.

You could add an estimation of those 3 variables without too much extra effort. Then real testing to see how far off the model is/is not. You need some data: averages of the reds and blues for that, then some averages on real fixtures to see how well the model works. If the averages are a bit off, you can then go back and add a correction factor to make up for that in the model.

A few step wise adjustments, I think it can work out fairly well to account for the other colors. Since many folks ALREADY have white/red/blue mixes in their fixtures, you just need some of their PAR data basically.

11-01-2014 05:34 AM

Hoppy

The calculator is based on using white LEDs only, and they tend to produce about the same lumens for every version of white. If you add in a lot of red/blue, etc, LEDs the calculator won't give good results. This is an empirical calculator, not a theoretical one. It is based on using a variety of data and finding an equation which works well enough with all of the data.

11-01-2014 12:57 AM

ybendek

Hello World

I'm newbie with LED fixtures and I want to change my current fixtures (T5) to LEDs, I have a planted tank with some carpet plants like Glossostigma elatinoides, Lilaeopsis brasiliensis and Hydrocotyle Tripartita, thus I understand that I will need a good PAR level. I found this awesome tool and I'm trying to use it and estimate a good configuration for my DIY fixture, but I'm a little confused :S

The first variable is "Lumens per LED".. as I understand the first part help me to calculate the PAR level per LED... so... what If I'm thinking to have a combination of LEDs like Cool White + Warm White + Royal Blue and maybe some deep or far red, normally every color comes with a different lumen range.. correct me if I'm wrong but some variable like "Number of LED rows" is assuming the same type of LED?

With a PC I think you do need to have Excel or Office installed to make the spreadsheet work. Without it, it is just a table in a document.

FYI for those not tethered to MS "Openoffice" Calc opens it just fine.. and that is free..

05-01-2014 05:36 AM

corlis

Comparison of LUX and PAR output for single colour LEDnm. Cyan, green, yellow LEDs have high LUX but low PAR while blues and reds have low LUX and high PAR. PAR graph shows the problem called the green valley issue in LED manufacturing

Is there a direct relationship between Lumen and PAR? I am not an expert, but I thought they are two different units, and things like spectrum play a role? Like having two LEDs with the same luminous flow, one with peaks in the yellow/green area, another one more in the red/blue photosynthetically speaking more significant area ?

Yes on all the questions. On Apogee's site there is a lumens to par conversion equation. There is a relationship but it's an approximation for white sun light. A par sensor will have a peak toward the blue.

03-18-2013 04:32 PM

Wasserpest

Is there a direct relationship between Lumen and PAR? I am not an expert, but I thought they are two different units, and things like spectrum play a role? Like having two LEDs with the same luminous flow, one with peaks in the yellow/green area, another one more in the red/blue photosynthetically speaking more significant area ?

03-18-2013 12:42 AM

m00se

I just tested it in Google Docs and it works. Make a new spreadsheet in GD and then go to File/Import and choose "New Spreadsheet" and point it to the xls file. It will upload it then you'll be good.

HTH

03-18-2013 12:07 AM

Hoppy

With a PC I think you do need to have Excel or Office installed to make the spreadsheet work. Without it, it is just a table in a document.

03-17-2013 10:54 PM

skanderson

i think it is because i dont have microsoft office installed does that sound right?

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